Wavelength division multiplexed (WDM) optical communication systems are known in which multiple optical signals, each having a different wavelength, are combined onto a single optical fiber. Such systems typically include a laser associated with each wavelength, a modulator configured to modulate the output of the laser, and an optical combiner to combine each of the modulated outputs.
Conventional WDM systems have been constructed from discrete components. For example, the lasers, modulators and combiners have been packaged separately and provided on a printed circuit board. More recently, however, many WDM components have been integrated onto a single chip, also referred to as a photonic integrated circuit (PIC).
Typically, the PIC includes active components that generate, amplify, and/or attenuate light, such as lasers, modulators, amplifiers, and variable optical attenuators (VOAs). Such active components often pass light from one to another over passive waveguides. The passive waveguides, however, introduce optical loss and occupy space on the PIC. As a result, the number of active components that can be integrated on the PIC, as well as overall device density, is limited.
PICs are typically manufactured by processing a semiconductor wafer, which is then diced or cleaved into individual die. By increasing device density, more die, and thus, more PICs may be obtained from a given wafer, resulting in reduced manufacturing costs. Accordingly, there is need for PICs having improved performance and lower fabrication costs.